title: Blood flow suppresses vascular Notch signalling via dll4 and is required for angiogenesis in response to hypoxic signalling.
abstract: OBJECTIVE
  The contribution of blood flow to angiogenesis is incompletely understood. We examined the effect of blood flow on Notch signalling in the vasculature of zebrafish embryos, and whether blood flow regulates angiogenesis in zebrafish with constitutively up-regulated hypoxic signalling.
  
  
  RESULTS
  Developing zebrafish (Danio rerio) embryos survive via diffusion in the absence of circulation induced by knockdown of cardiac troponin T2 or chemical cardiac cessation. The absence of blood flow increased vascular Notch signalling in 48 h post-fertilization old embryos via up-regulation of the Notch ligand dll4. Despite this, patterning of the intersegmental vessels is not affected by absent blood flow. We therefore examined homozygous vhl mutant zebrafish that have constitutively up-regulated hypoxic signalling. These display excessive and aberrant angiogenesis from 72 h post-fertilization, with significantly increased endothelial number, vessel diameter, and length. The absence of blood flow abolished these effects, though normal vessel patterning was preserved.
  
  
  CONCLUSIONS
  We show that blood flow suppresses vascular Notch signalling via down-regulation of dll4. We have also shown that blood flow is required for angiogenesis in response to hypoxic signalling but is not required for normal vessel patterning. These data indicate important differences in hypoxia-driven vs. developmental angiogenesis.
authors.affiliation: Lab D38, MRC Centre for Developmental and Biomedical Genetics, University of Sheffield, Firth Court, Sheffield S10 2TN, UK.
authors.forename: Oliver
authors.initials: O
authors.lastname: Watson
authors.forename: Peter
authors.initials: P
authors.lastname: Novodvorsky
authors.forename: Caroline
authors.initials: C
authors.lastname: Gray
authors.forename: Alexander M K
authors.initials: AM
authors.lastname: Rothman
authors.forename: Allan
authors.initials: A
authors.lastname: Lawrie
authors.forename: David C
authors.initials: DC
authors.lastname: Crossman
authors.forename: Andrea
authors.initials: A
authors.lastname: Haase
authors.forename: Kathryn
authors.initials: K
authors.lastname: McMahon
authors.forename: Martin
authors.initials: M
authors.lastname: Gering
authors.forename: Fredericus J M
authors.initials: FJ
authors.lastname: Van Eeden
authors.forename: Timothy J A
authors.initials: TJ
authors.lastname: Chico
mesh_terms: D000818:Animals; D001775:Blood Circulation / Q000502:physiology*; D003931:Diacetyl / Q000031:analogs & derivatives / Q000494:pharmacology; D000860:Hypoxia / Q000503:physiopathology*; D047908:Intracellular Signaling Peptides and Proteins / Q000235:genetics / Q000502:physiology*; D008565:Membrane Proteins / Q000235:genetics / Q000502:physiology*; D018919:Neovascularization, Physiologic; D051880:Receptors, Notch / Q000502:physiology*; D015398:Signal Transduction / Q000502:physiology*; D025521:Tumor Suppressor Proteins / Q000502:physiology; D040301:Vascular Endothelial Growth Factor Receptor-2 / Q000502:physiology; D015027:Zebrafish / Q000196:embryology; D029961:Zebrafish Proteins / Q000502:physiology
chemical_list: D047908:Intracellular Signaling Peptides and Proteins; D008565:Membrane Proteins; D051880:Receptors, Notch; D025521:Tumor Suppressor Proteins; C542158:Vhl protein, zebrafish; D029961:Zebrafish Proteins; C064045:delta protein; C004717:diacetylmonoxime; D040301:Vascular Endothelial Growth Factor Receptor-2; D003931:Diacetyl
keywords: Angio-/arteriogenesis; Angiogenesis; Blood flow; Notch; Zebrafish